This invention relates to a tool clamping device for a machine spindle, where said tool clamping device includes a drawbar, at one end of the drawbar a clamping organ is arranged in order to clamp part of a tool coupling at said end, plus a device to exert an axially directed force on the drawbar in a direction away from the clamping device, where the device which is to exert a force on the drawbar includes a housing, a piston which can be displaced axially in the housing plus a compressible pressure medium in the housing. The invention also relates to a machine spindle.
Reference is made to the attached FIG. 1A and the associated descriptive section below for a more detailed explanation of the prior art.
A primary object of the present invention is to present a tool clamping device for a machine spindle which is completely symmetrical and thereby to a large degree free from vibration.
A further object of the present invention is to present a tool clamping device which is capable of withstanding more clamping cycles than the prior art.
An additional object of the present-invention is to reduce the axial length of the tool clamping device, more exactly to reduce the length by approximately 50%.
A further object of the present invention is that the tool clamping device should be easier to assemble in the casing of the machine spindle.
The objects of this invention have been achieved through a tool-clamping device, which comprises a drawbar that is moveable in an axial direction, and a clamping unit operably connected to a first axial end of the drawbar and arranged to be displaced to clamping and non-clamping positions in response to axial movement of the drawbar in clamping and non-clamping directions, respectively. A force-exerting unit is provided for exerting an axial force on the drawbar in the clamping direction. The force-exerting unit includes a housing, a piston disposed in the housing and connected to the drawbar adjacent a second axial end thereof, and a compressible gaseous pressure medium in the housing for biasing the piston in a direction for moving the drawbar in the clamping direction.
The invention also pertains to a machine spindle which includes a casing in which the clamping device is disposed, as well as a push rod for axially displacing the drawbar.